Automatic density control for classifiers



M y 22, 5 c. SHAPL'EY, JR 2, 7 ,8

AUTOMATIC DENSITY CONTROL FOR CLASSIFIERS Filed Jan. 4, 1944 2 Sheets-Sheet 1 May 22, 1945. O SHAPLEY, JR 2,376,825

AUTOMATIC DENSITY CONTROL FOR CLASSIFIERS Filed Jan. 4, 1944 2 Sheets-Sheet 2 Patented May 22, 1945 AUTOMATIC DENSITY CONTROL FOR CLASSIFIER-S i Cooper Shapley, Jr., S :a li da, C o lo.' ,i Application January 4, 1944,- Serial'No. 516,984

V a H t 16 Claims. This invention relates to improvements in wet material classifiers, and more specifically to automatic pulp density control means for the discharge of a constant density pulp from the,

classifier 'by means of a floating bafile. In any wet classifier apparatus, the top film of pulp overflowing the weir is very dilute and of low density, while afew inches below the surface the pulp is much more dense and of ahigherspecific gravity. l

Classifierson which this improvement is applicable are generally of the rake or spiral type and usually comprise: elongated tanks into which is constantly admitted material which has been groundin admixture with water by a-ballmill to provide the desired pulp. This pulp is delivered to such a tank by means of a launder interconnecting the tank and mill, and includes certain recovered material which is constantly being returned to the ball milljorregrinding by means of another launder interconnecting same. Iheprocess is thuscontinuous with a constant recovery of the properly sized, material as finished product. Generally, this pulp, consisting of ground material. and water, is admitted near the lower end of the tank and permitted to fiow or spill over that en'd with a consequent continuous separation of the properly sized particles as a finished product. p t

While the material is ground in the ball mill to a predetermined maximum coarseness, the ground material as a wholewill comprise variable sized particles ranging from that of the maximum coarse grind to very much smaller particles It is to be particularly notedat this point, that the material comprising the pulp is thus variable, comprising particles o f substantiallyl different specific gravity-and that many of the larger particles of this pulp may be much lighter than smaller particleswhich are more valuable and which it is desired to eventually recover in the flotation process.

The object soughtin the use of present classifiers is therefore to separate the lighter particles which will remain in suspension longer and will be carried up and spilled over the discharge end or weir of the tank, while the heavier particles settle to the bottom and are recovered from the classifier tank as above explained.

regrinding, for use in subsequent pulp in the.

With the classifiers, or separators now in use,

mechanicaladjustments are reliedupon for conspecific gravity, such as by increasing or decreasing the speed of the mechanism, increas ing or decreasing the density ofthe pulp, changing the inclination of the tank bottom, and/or changing the distance between the bottom of the tank and rakes or other conveyor means. While such" adjustments obviously alter the weight of the separated particles, generally, they are far from being 'criticaland necessitatetime and labor to operate and adjust each time it maybedesirab-le to regulate the pulp density or keep it uniform With the above general construction in view, the primary object of the invention is the-provision of means for maintaining the pulp which flows or spills over 'the weir at the discharge end of the tank, at a substantially constant density or'specific gravity.

A further object of=my invention is the provision of a classifier tank having a baille which is constructed and arranged to float in the-pulp adjacent-the discharge end of the tank, the;

baflie being adapted to rise and fall automatically in the tank according to changes in densityiof. the pulp atthe lower edged the bafile'so. as to causedilute surface pulp to pass under the lower edge cfthe ,baflie and thus help to carry over,

the weir, the denser and higher specific gravity material found at the desired depth :below the 5 surface of the classifierpulp.

lieving fthe. classifier and grinding apparatus of further handling this material.

A still further object ofImy invention is theprovision of such an automatic baffle for uni-- formly controlling the density of the pulp at the 40 overflow. end of the tank, in which the baffle maybe set for any desired pulp density discharge to obtain the most eificient operation of the classifier, and when once set will. automatically maintain the pulp at the overflow at a predetermined density. I Another object of my invention is the pro-,

vision of an automatic overflow control battle for classifiers or other pulp separating tanks, which may be manually set or adjusted at will toautomatically maintain its lower edge sub-f merged to a predetermined density point within a the pulp'according, to the density of the pulp at that point where the larger waste particles, of

. lessspecific gravity would accumulate, whereby trolling the separation of particles of given 56 to'insure constant separation of said larger waste pivoted on the sidewalls l3 of the tank intermediate its-ends, as at 28; Thls' lever bar is providedat its front end'with a dependingbaflie" plate"!!! which extends into the pulp P and a buoyancy member 29* is providedas in Fig. 2A. As indicated in Fig. 4 the density of the pulp P gradually increases from the top level lto the.

bottom of the tank, and as the flow of the pulp is in the direction of-the overflow lip I6, the

density of the pulp spilling over the lip will always the lip H; the lever arm 21 may beadjusted; to"

rockon itspivot 28 as by means of one or more weights 29 These weights may be positioned as shown in solid or dotted lines in Fig. 3. Hence, if the lever arm is weighted'at the left of the pivot 28 the bafile 29 will be raised with' a corresponding, reduction in specifiogravity of the pulp body spilled over the. lip IE, while if the lever arm is weighted atthe right of the pivot .28, the baflie 28 will .fall; with a corresponding increase in the specific'gravityof the pulp, body spilled over the lip. I

A further form of pulp flow control means takes the form illustrated in Figs. 5, 6 and 7. Thisembodiment of the invention comprises a pair of supporting arms 30 which are adapted for pivotal support adjacent their rear ends on a pivot bar 3 supported upon opposite sidewalls of the tank Ill. The forward ends of the arms30 are secured as rby braces .32 to a crossbar 33 extending parallelgwith, the supporting onpivot bar 3| Secured to the bar 33 at its upper edge as'by securing devices 34 is a thin metallic plate or baffle 35..

The lower edge of the plate: 1 5 is secured to a plurality of parallel and laterally spaced buoy, ancy bars 36. .In this form washers 31 are preferably employed to maintain the vertically extending bars 36in parallel laterally spaced relation, and a plurality of bolts 38 extend through the plate 35, bars 35 and washers 3''! for rigidly maintaining'same in this. position. The bars 36 and washers 3'! may be hollow or constructed of wood and the upper sides of the bars are preferably bevelled, as indicated, to avoid loading as by collection of sand or other material thereon.

While but three spaced buoyancy bars 36 are is always substantially small.

As indicated in Fig. 5 the arms 30 maybe provided with a plurality of cooperating pivot notches 4!) for varying the depth of submersion.

of the bars 36 as well as its relation to the front wall I2 of the tank. An application of the structure of Figs, 5 and 6 to the pulp tank In is illustrated in Fig. 7, wherein it will be observed that the bars 36 are submerged in the pulp and at the desired level where they will automatically adjust off'the pulp at that point;

AS in Figs. 5 and a, the top bevelled'walls'or the bars 36wi1l preclude the collection-of settling: ,material thereon. v

' While I have disclosed several specificstructural embodiments of my invention, it is --to: be particularly noted that the principle of operation is'the same with each, that is, the automatic density control of theflow ofpulp over the classifier spillway or lip I6 is predetermined and niain tai'ried; i. 'e.-thespecific gravity of the pulp spilling" from the-settling tank; over the lipls-is'alwaysf.

equal to that at the bottom of the adjustable the density of the pulp onfthe surface.

automatically-operable bafile,and not equal to It is to be understood that'the specific embodi men'ts ofthe invention disclosed are illustrativeonly and notrestrictive, the scopeof the inven'f tion being definedi'n the subjoine'd claims;

tacle to'which ground material and water in the form of pulp is constantly delivered and from which the properly sized "materialisconstantly erlysizedmateri'al constantly flows; the improve merit which comprises an 'imperiorate, freely movable bafifle extending transverselyfacross the receptacle from a point aboveto, a point below the liquid level and adjacent the overflow-from 'therecepta'cle, said b'aflie-beihg mounted for fig? vertical movement in the rec'eptaole, and means associated with the baflie and immersed in the materiallin the receptacle for automatically mov-- ing and supporting the b aille inaccordance with ehangesin the, density of the pulp in the receptacle as constantly delivered thereto for main taining the pulp flowing over the lip at a constant e si -1., .1. A 2. Flow control means for use with a classifier which includes an elongated tank through which a pulp consisting of ground material and Water" constantly flows, and a'lip at one end of the tank; overwhich the'pulp flows at thellevel thereof in the, tank; comprising an imperforate buoyant bajfile for vertical disposition within the tank and extending throughout substantially the width thereofadjace'nt to but spaced'from theoverfiow lip, the baflle being free to move vertically within.

with the floating baffle for varying the depth to which the baffle is submerged in the pulp at any density thereof.

4. Flowcontrol means according to claim 2, wherein said 'bafile includes a buoyancy member for submersion in the pulp, a vertical plate supporting said member at the lower edge thereof, lever arms connected at corresponding ends thereof to the plate. and means for pivotally supporting the armsadjacent the other ends on the tank.

'5. In combination with the settling tank of .a classifier having at one end thereof a lip over which flows a constantly moving pulp consisting of ground ore and water, means movably supported by the tank and having a part providing a the batlle plate 35 inaccordancewiththe density floating iimpertoratea. Dame-1 entendingjacrossi thc+ tank. to provide a flow restrictingibaffle: adjacentseidiii randextending pax'tisllyr'into the-pulp, said part beingbuoyed? up by the speciflctgravity-ofzthe pulp and beingthereby automatically adjustable to provide a: constantv density oflthev pulp flowing over; said lip. 1

. 6.: Thestructure accordingto claim wherein- Y said. means comprises; a lever arm; pivotally sup 1 ported intermediate its ends- 011 thersi'de-uwall y ofmenswear v tlingstanh havingsidewalls azdownwardlyi inw a c1ined,- -.bottom;wa11 and a" back. wall, means ion deiivering'g-roundzoreand-water into thersaid tank for providingv a pulp, the back wailihavingyanz overflow lip forrrecovering the properly sized orew particles? of the pulp: flowing thereover,.- the improvement comprising .a pair of-iever armspivot x' ally. supported adj acent" their rear ends on i said; side walls, and a verti-callydisposed-floating im.-- perforaterbaflie carried bythe forwardendsofthe arms andlextending.substantiallythe-widthiofthe 'ta-nk j in spaced.- relatiomto said back wall' -thei pulp flowswver ailip at one end of the tank,

means; for" providing; er;- constant density in the 1 pulp, flowinggover; theelip comprising a. vertically,

I disposed floating imperforate: bafiie extending v throughout? substantially the width oi thee tank and in spaced relation. to the-lip, said:baflie;-hav-- Jing a floatat-its; lower edge. disposed-for. submergencein the pulp and-being;free to be buoyed neathi-the lower. submerged edge oi the baflieup ward/between same and the adjacent end of the tang-and ithencegoverithe= overflowlip, whereby lower edge otthejbafii'e including afloat extending-s into I the pulpfrom a point above the pulp K level;

and being buoyedltherebvaboutsaid pivotal" supi port whereby theibaflie rises or fallstmeccordance, 1

with the densityioi the 'pulp for rnaintaiming. a constant density v ofithe pulp flowing-therebeneathqendloversaidllifl. v

,121 The structure according to claim If to gether with meansjfor increasing-.01 diminishing! the extent off submergence "of the noatmgiBaflie-j with a correspondinglchange in the density ofthe' pulp, flowing over thelip; 3 7

7 13';- The structure accordingto cIaiin I'1' where;-

in said floating baffie comprises. althin"mtallic I plateand; the float-comprisesa luraiity of aral;

Y the over-410w pulp is I automatically maintainedat a. constant density duettor-the depth to which;

theipulpvaries. V

.81 The structure according toiclaifmi 7; together:

the b afiie W111i sink. or. raise as specific. gravity: of

' witiilmeans forivaiiyingithe .extent-ofisuh'mer'gence offthe..fioatingbaflieintheipulp foncorrespondingly varyingithe density ofjthe-pulp flowing over.

plate. having a Tower edge ortion thereof Bent" v n. 40 saidiioatingbaflie is supported by. one end-ofaua v levee arm. pivotally supported intermediate its ends onsaidtank." p a 1'0'.. 'I'hevstructure according to'claim 7'fwherein tanksand means for varying. the depth of sup- -merge'nce o'fthefioatingQbaffle in the pulp. a; classifier comprising anelongated setlelspaced buoyancy bar secured to the; lower edge of the plate, the'upper edges'of said bars being bevelled" to prevent" acciimulation of mat'eriai thereon I U I4 The-structure according to tie-1m 1' 1 whereplate'andhaving 1'6: The" structure according to claim Irwher; in: said floating: baffle comprises nietallic I p1a;tei having lower edge portion thereof oent uponthe' hody thereof: amddefiningwitnth of th'e plate" an airchamber whose opposite-e are clos'edi and the-supper wall cr me-air chamber being ati-an acute: angle to the plate. I

' CQOPERQ'SHAPLEY; Jr; 

